Methods

The present study included 225 consecutive patients referred to a cardiac rehabilitation program, 1 month after an acute myocardial infarction. Exclusion criteria were age >75 years, inability to exercise, severe valvular heart disease, moderate or severe chronic lung disease, atrial fibrillation, or exercise-induced myocardial ischemia. All patients were prospectively enrolled and were submitted on the same day to clinical evaluation (performed by a cardiologist), anthropometric evaluation, detailed transthoracic echocardiography, computed tomography (CT) scan, and blood sample collection. The investigation conforms to the principles outlined in the Declaration of Helsinki and was approved by the institution’s ethical committee. All patients gave their written informed consent.

Measurements included height, weight, and waist circumference. Body mass index (BMI) was calculated for each subject. Waist circumference was measured at the midpoint between the iliac crest and the lower rib margins, in the midaxillary line. According to World Health Organization criteria, overweight was defined as BMI between 25 and 30 kg/m ² and obesity as BMI >30 kg/m ² . Abdominal obesity was defined as waist circumference >102 cm in men and >88 cm in women. Hip-to-height and waist-to-height ratios were calculated as the ratio between hip circumference (cm) or waist circumference (cm), respectively, and height (m). Body composition was assessed by bioelectrical impedance analysis (Tanita Corporation, Arlington Heights, Illinois) to determine body fat percentage (%).

All echocardiographic studies were acquired by a single experienced cardiologist using an ultrasound system (iE33, Philips Medical Systems, Best, The Netherlands) equipped with an S5-1 transducer. Images were digitally stored for posterior offline analysis. Cardiac chambers dimensions; volumes, and LV mass were measured according to current recommendations. Mitral inflow velocities were assessed using pulse-wave Doppler in the apical 4-chamber view, with a 3 mm sample placed between the tips of the mitral leaflets; velocities were recorded at end expiration and averaged over 3 consecutive cardiac cycles. Pulse-wave tissue-Doppler velocities were acquired at end expiration, in the apical 4-chamber view, with the sample positioned at the septal and lateral mitral annulus. Pulse-wave Doppler velocities at the upper right pulmonary vein were also recorded. For all parameters the average of 3 consecutive heartbeats was recorded.

Diastolic function was assessed according to the recent consensus guidelines on diastolic function evaluation by determining peak early (E) and late (A) diastolic mitral inflow velocities; deceleration time of early LV filling (DT); the E/A ratio; the septal, lateral and average myocardial annular tissue velocities (E′ sep, E′ lat, and E′ mean, respectively); the E/E′ ratio (septal, lateral, and mean E/E′); pulmonary vein flow analysis (to calculate the Ard-Ad difference: the time difference between the duration of the atrial reversal wave of the pulmonary flow–Ard–and the mitral A-wave duration–Ad); and isovolumic relaxation time. Using the recent European Association of Echocardiography/American Society of Echocardiography guidelines on diastolic function evaluation, patients were categorized in diastolic dysfunction grades normal, grade I (mild diastolic dysfunction), grade II (moderate diastolic dysfunction), and grade III (severe diastolic dysfunction) by 2 independent cardiologists who were blinded for the study data. In case of discordance, each case was discussed individually, and if doubt persisted no grade was endorsed, which happened in 20 patients (8.9%).

Multidetector CT scans were performed in all patients using a 64-slice CT scanner (SOMATOM Sensation 64, Siemens Medical Solutions, Forchheim, Germany) with 2 different acquisitions: 1 for abdominal fat quantification and the other for epicardial adipose tissue quantification. To assess abdominal fat, a single-slice abdominal CT scan was performed between L4 and L5, according to the method described by Borkan et al. The scan parameters were 120 kV and 216 mA with 5 mm thickness. This resulted in an estimated radiation exposure of 0.06 mSv. On the scan obtained, a cursor pointer was used to trace the abdominal visceral fat area, and the data were processed using a histogram-based statistical program according to the previously described method. One expert, unaware of the patient’s details, measured abdominal fat distribution. Fat tissue was defined in the range between −150 and −50 Hounsfield units. Total abdominal fat area was measured and subcutaneous fat area was obtained by subtracting abdominal visceral fat from the total abdominal fat area.

An experienced radiographer, blinded for the purpose of the study and the patient’s anthropometric data, quantified epicardial fat volume (EFV). A cursor pointer was used to manually trace the pericardial contour using 1 mm-thick reconstructed axial slices. Pericardium contour was traced for every 10 mm, starting from the lower visible level of pulmonary artery bifurcation until the top level of the pulmonary valve, for every 20 mm from there until the first slice where the diaphragm becomes visible and again for every 10 mm from this point until the last slice where pericardium is still visible, as illustrated in Figure 1 . The pericardium contour was extrapolated by the software, syngo Volume (Siemens Medical Solutions, Inc) for the nontraced slices and rechecked by the operator. Within these anatomical limits, EAT was identified using the adipose tissue attenuation references (from −150 to −50 Hounsfield units) and a final EFV resulted from the sum of all slices of fat values.

Measurement of EFV by CT. The level of the axial slices used for pericardial delineation is shown in a coronal projection. EAT was identified within the limits of pericardium sac using the adipose tissue attenuation references (−50 to −150 Hounsfield units). Pericardium contour was traced for every 10 mm, starting from the lower visible level of pulmonary artery bifurcation until the top level of the pulmonary valve; for every 20 mm from there until the first slice where the diaphragm becomes visible; and for every 10 mm from this point until the last slice where pericardium is still visible. Final EAT volume quantification was calculated as the sum of all slices fat values.

Statistical analysis was performed with SPSS program version 20 (IBM Corp, Armonk, NY). All continuous variables are shown as a mean ± SD for normally distributed variables or as a median and interquartile range for non-normally distributed variables. Categorical variables are expressed as a number (n) and percentage (%). Statistical significance was defined as p <0.05. Pearson and spearman correlation coefficients (r), as appropriate, were analyzed to access the correlations between cardiac function and structure echocardiographic and adiposity parameters obtained by anthropometry and CT scan. To compare median values of several adiposity parameters according to diastolic function grades, nonparametric tests were used (Mann-Whitney and Kruskal-Wallis tests, accordingly). Linear regression analysis was performed for univariate and multivariate analyses of fat distribution variables that predict worse diastolic function. Multivariate analysis was performed accordingly with adjustment for age, hypertension, gender, and several fat depots.

Results

The clinical, anthropometric and analytical characteristics of the study population are listed in Table 1 . Most patients were men (84%), with a mean age of 55.1 ± 10.9 years, 47.6% were overweight and 20.9% were obese. The mean ejection fraction was 53.6 ± 9.3% and most patients (64.4%) had some degree of diastolic dysfunction. As listed in Table 2 , there was a significant correlation between BMI and decreased early diastolic velocity (E′ lateral) and increased LV filling pressures (E/E′ mean). Fat-mass percentage, assessed by bioelectric impedance analysis, was also inversely correlated with E′ septal velocity, E′ lateral velocity (as shown in Figure 2 ), and E/E′ mean ratio. In contrast, as listed in Table 3 , there was a significant increase in fat-mass percentage, according to the classification in diastolic dysfunction grades (p for trend <0.01). After multivariate analysis, with adjustment for age, gender, and hypertension history, the association between fat-mass percentage and early diastolic velocities (E′ septal and lateral) remained significant, as listed in Table 4 .

Scatter plots showing the association between several adiposity parameters and diastolic function, assessed by E′ lateral velocity. r = correlation coefficient between the 2 variables.

Table 4

Univariate and multivariate linear regression analyses for the association of diastolic function parameters (E’ velocity and E/E’ ratio) with adiposity parameters

	E’ septal velocity				E’ lateral velocity		E/E’ ratio
	Crude β (95% CI)	Adjusted β ∗ (95% CI ∗ )	p value ∗	Crude β (95% CI)	Adjusted β ∗ (95% CI ∗ )	p value ∗	Crude β (95% CI)	Adjusted β ∗ (95% CI ∗ )	p value ∗
BMI	-0.05 (-0.10 to 0.00)	-0.05 (-0.09 to -0.01)	0.02	-0.08 (-0.16 to -0,01)	-0.09 (-0.16 to -0,02)	<0.01	0.09 (-0.03 to 0.20)	0.10 (-0.01 to 0.22)	0.08
Fat mass %	-0.06 (-0.09 to -0.03)	-0.04 (-0.07 to 0.00)	0.04	-0.09 (-0.14 to -0.04)	-0.08 (-0.13 to -0.02)	<0.01	0.09 (0.01 to 0.16)	0.08 (-0.02 to 0.17)	0.11
WP/height	-0.09 (-0.13 to -0.05)	-0.05 (-0.09 to -0.01)	0.02	-0.13 (-0.19 to -0.07)	-0.09 (-0.15 to -0.03)	<0.01	0.11 (0.02 to 0.21)	0.09 (-0.01 to 0.19)	0.07
Total abdominal Fat (x10)	-0.03 (-0.05 to -0.01)	0.02 (-0.04 to 0.00)	0.07	-0.05 (-0.07 to -0.02)	-0.03 (-0.06 to 0.00)	0.03	0.04 (0.00 to 0.09)	0.04 (-0.01 to 0.08)	0.09
Subcutaneous abdominal fat (x10)	-0.02 (-0.05 to 0.01)	-0.02 (-0.05 to 0.00)	0.23	-0.03 (-0,08 to 0.01)	-0.04 (-0.08 to 0.00)	0.07	0.04 (-0.03 to 0.11)	0.04 (-0.03 to 0.11)	0.25
Visceral abdominal fat (x10)	-0.06 (-0.09 to -0.03)	-0.03 (-0.06 to 0.01)	0.15	-0.10 (-0.15 to -0.05)	-0.05 (-0.10 to 0.00)	0.04	0.08 (0.001to 0.16)	0.08 (0.00 to 0.16)	0.06
Epicardial fat (x10)	-0.11 (-0.17 to -0.06)	-0.06 (-0.12 to -0.01)	0.02	-0.17 (-0.25 to -0.09)	-0.11 (-0.19 to -0.03)	<0.01	0.19 (0.07 to 0.31)	0.19 (0.06 to 0.32)	<0.01

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